West Nile Virus Confirmed in Two B.C. Horses

Friday, September 11, 2009 07:27 PM

B.C. has confirmed its first locally acquired cases of West Nile virus in horses. This closely follows the confirmation of the first human cases, further indicating the presence of West Nile virus in the province.

It has been confirmed that a horse in the Fraser Valley and a horse in the South Okanagan of the Interior Health region have been infected with West Nile virus. Test results are pending on another horse in the South Okanagan. None of these animals have travelled outside the province. In 2006, a horse that had travelled to Colorado was infected with West Nile virus before returning to BC.

"This is not a surprising development," said Dr. Paul Kitching, chief veterinarian and branch director at the Animal Health Centre. "British Columbia has long anticipated the arrival of West Nile virus, and now it's in multiple regions of the province. What is important is
preventing infection as best as possible, for both humans and animals. Of all large land mammals, horses are particularly susceptible. There are West Nile virus vaccines for horses, and horse owners should talk to their vets about getting their animals immunized."

West Nile virus is a mosquito-borne illness. Mosquitoes become infected with the virus after feeding on infected wild birds and then transmit the virus through bites to people, animals and other birds. Some animals infected with West Nile virus may show no signs. Others
may exhibit a range of symptoms including fever, muscle spasms, weakness, lack of co-ordination, seizures and changes in behaviour. For horses, signs of West Nile virus infection may include stumbling, weakness, head pressing, confusion, inability to stand, seizures and
listlessness. Most horses recover fully. In severe cases, horses may die or need to be euthanized.

Most people who are infected with West Nile virus will have no symptoms at all. However, about 20 per cent of people infected will develop an illness with fever, headache and rash symptoms. In about one in 150 human cases, more severe neurological complications can
occur, such as encephalitis (inflammation of the brain) and meningitis (infection of the lining of the brain).

West Nile virus cannot be transmitted directly from an infected horse to humans. Horses that have been infected are not a direct risk to other horses in the area. However, cases in horses signal that infected mosquitoes are present in the area, which indicates a risk to
other horses and people in the vicinity.

In addition to getting their animals vaccinated, horse owners should make an effort to drain standing water where mosquitoes may breed and practise mosquito control in general.

"While there are West Nile virus vaccines for horses, there is currently no vaccine for humans," cautioned Dr. Bonnie Henry, director of the Vector-Borne Disease Program at the British Columbia Centre for Disease Control, an agency of the Provincial Health Services
Authority. "Common-sense precautions against getting bitten by mosquitoes should be taken, especially when outdoors, and even as we head into the fall. This includes wearing light-coloured, long-sleeved shirts and long pants - especially in the evenings and early mornings when mosquitoes are most active - and using mosquito repellents that are federally registered, such as those that contain DEET and lemon eucalyptus oil."

"This is the first confirmed West Nile activity in the Fraser Health region," confirms Dr. Elizabeth Brodkin, medical health officer for Fraser Health. "We have a well-established surveillance program in the Fraser Valley, and so far we have had no positive mosquitoes or birds
in the area. But the case of this infected horse indicates that the virus is here. We are reminding people in the Fraser Health region to continue to take precautions to prevent mosquito bites as the best way to protect themselves and their families from West Nile virus."